The objectives of this study are to characterize the biochemical, morphologial and functional responses of central noradrenergic neurons in response to axonal injury and sprouting. Primarily it will seek to determine if (a) during the retrograde reaction in noradrenergic neurons of the locus coeruleus induced by hypothalamic lesions transecting noradrenergic axons there is a selective decrease in the synthesis of specific proteins required for the biosynthesis of the neurotransmitter norepinephrine, including the enzymes tyrosine hydroxylase and dopamine-Beta-hydroxylase, (b) if the retrograde responses parallel sprouting from damaged central noradrenergic fibers, (c) if there are any demonstrable ultrastructural correlates of biochemical changes during the retrograde response in neurons in locus coeruleus, and (d) if the retrograde response is a concomitant of regeneration or of injury. It will also determine if the recovery of the behavioral deficits in feeding and aggression resulting to damage of central noradrenergic axons in the hypothalamus correlates with the regenerative processes in central noradrenergic neurons. BIBLIOGRAPHIC REFERENCES: Reis, D.J., Hoh, T.H. and Ross, R.A.: Effects of reserpine on activities and amounts of tyrosine hydroxylase and dopamine-Beta-hydroxylase in catecholaminergic neuronal systems in rat brain. J. Pharmacol. Exp. Ther. 193: 775-784, 1975. Joh, T.H., Shikimi, T., Pickel, V.M. and Reis D.J.: Brain tryptophan hydroxylase: purification of, production of antibodies to, and cellular and ultrastructural localization in serotonergic neurons of rat midbrain. Proc. Nat. Acad. Sci. USA, 72: 3575-3579, 1975.